fix: Add update_timestamp_tz property to StorageSession

This property is a compatibility alias that returns the update timestamp as a POSIX timestamp. It infers whether the database is SQLite using sqlalchemy.inspect to call get_update_timestamp correctly

Close #4334

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 864595914

src/google/adk/sessions/schemas/v0.py

@@ -38,6 +38,7 @@ from google.genai import types
 from sqlalchemy import Boolean
 from sqlalchemy import ForeignKeyConstraint
 from sqlalchemy import func
+from sqlalchemy import inspect
 from sqlalchemy import Text
 from sqlalchemy.dialects import mysql
 from sqlalchemy.ext.mutable import MutableDict
@@ -130,6 +131,20 @@ class StorageSession(Base):
   def __repr__(self):
     return f"<StorageSession(id={self.id}, update_time={self.update_time})>"
 
+  @property
+  def update_timestamp_tz(self) -> float:
+    """Returns the update timestamp as a POSIX timestamp.
+
+    This is a compatibility alias for callers that used the pre-`main` API.
+    """
+    sqlalchemy_session = inspect(self).session
+    is_sqlite = bool(
+        sqlalchemy_session
+        and sqlalchemy_session.bind
+        and sqlalchemy_session.bind.dialect.name == "sqlite"
+    )
+    return self.get_update_timestamp(is_sqlite=is_sqlite)
+
   def get_update_timestamp(self, is_sqlite: bool) -> float:
     """Returns the time zone aware update timestamp."""
     if is_sqlite:

src/google/adk/sessions/schemas/v1.py

@@ -26,11 +26,11 @@ from __future__ import annotations
 from datetime import datetime
 from datetime import timezone
 from typing import Any
-from typing import Optional
 import uuid
 
 from sqlalchemy import ForeignKeyConstraint
 from sqlalchemy import func
+from sqlalchemy import inspect
 from sqlalchemy.ext.mutable import MutableDict
 from sqlalchemy.orm import DeclarativeBase
 from sqlalchemy.orm import Mapped
@@ -105,6 +105,20 @@ class StorageSession(Base):
   def __repr__(self):
     return f"<StorageSession(id={self.id}, update_time={self.update_time})>"
 
+  @property
+  def update_timestamp_tz(self) -> float:
+    """Returns the update timestamp as a POSIX timestamp.
+
+    This is a compatibility alias for callers that used the pre-`main` API.
+    """
+    sqlalchemy_session = inspect(self).session
+    is_sqlite = bool(
+        sqlalchemy_session
+        and sqlalchemy_session.bind
+        and sqlalchemy_session.bind.dialect.name == "sqlite"
+    )
+    return self.get_update_timestamp(is_sqlite=is_sqlite)
+
   def get_update_timestamp(self, is_sqlite: bool) -> float:
     """Returns the time zone aware update timestamp."""
     if is_sqlite: